(a) Brachyodont:

(b) Hypsodont:

In large grazing mammals teeth are elongated,prism shaped with high crown and low
roots.e.g.,Horse.

Structure of teeth

Teeth divided into three parts-

(i)Root:

Inner most,attached to the bone with the help of cement(hyaluronic acid).

(ii)Neck:

Middle,small covered with gum.Gum provides strength to the teeth.

(iii)Apex or crown:

External exposed part of teeth.Longest part,white in colour.

A small cavity present inside teeth called as pulp cavity or dentine pulp cavity.It contains
blood vessels,lymphatic vessels,nerve fibres,connective tissue etc.and provides nutrition to
odontoblast cells or osteoblast cells.The odontoblast cells are mesodermal in embryonic
origin forming immediate covering of the pulp cavity.The cells secrete dentine/ivory.Bulk
of tooth in a mammal is formed of dentine.Dentine is a layer of inorganic substances
(62-69%),which surrounds the odontoblast cells.It is mesodermal in origin.Enamel,secreted
by Ameloblast/Enameloblast cells,forms the outermost covering,It is ectodermal and made up
of 92% of inorganic substances,hence considered as hardest part of the body.The inorganic
substances present are [Ca3(PO4)2,
Ca(OH)2.H2O] Calcium phosphate(85%),Calcium hydroxide and
Calcium Carbonate.Cement/Cementum attaches the tooth root to the bone.

Dental formula:

Each mammalian species is characterized by its own specific dentition with a definite
number and arrangement .Hence ,dentition is of taxonomic importance.

Oesophagus(food tube)

1.Morphology:

Single,ectodermal ,dorsal to trachea, approximately 25cm long,passes through thoracic
cavity and opens into stomach present in abdominal cavity.Oesophagus anteriorly opens into
pharynx through gullet and posteriorly into stomach through cardia orifice.

Histology:

Serosa is absent but outermost layer of connective tissue is called as tunica adventitia.
Muscular layer are striated/voluntary in anterior region and unstriated /involuntary in posterior
part.The epithelial lining is made up of non-keratinized stratified squamous epithelial cells.
Goblet cells are present.

Oesophagus lack digestive glands but multicellular glands are found,which extends upto
submucosa of oesophagus is thickest than other parts of alimentary canal.